This system for real-time localization of a millimetric or submillimetric object, such as a microrobot, in a viscoelastic medium, in particular in an organ of a subject such as a brain, a liver or a pancreas, includes: at least one bubble configured to be attached to said object, the or each bubble having a hermetic envelope filled with a gas; at least one ultrasound transducer configured to emit initial ultrasound signals and to detect deflected ultrasound signals deflected at the surface of the bubble(s); a processing unit in communication with the ultrasound transducers and configured to generate localization data of the object from localization data of the bubble(s) based on the deflected ultrasound signals detected by the ultrasound transducers.